Most traditional absorbent structures consist of a static network of fibers that contain a plurality of open areas located between the fibers. The open areas retain aqueous fluid that is absorbed by the absorbent structure. The majority of fluid is not absorbed into each individual fiber but instead most fluid is retained within the empty spaces that are formed in the network of cellulosic fibers. If the traditional absorbent member has a high absorbent capacity it usually does not have a high wicking rate. The reason for this is that the first attribute is in conflict with the second attribute.
Efforts to find absorbent members which have both a high absorbent capacity as well as a high wicking rate have only been marginally successful. It has been recognized that the dynamic properties of the fibers themselves somehow have to be changed. Some success has been obtained in calendering a wet laid network of bleached chemi-thermo-mechanical pulp (BCTMP). For this material, small expansion or release of potential energy upon wetting of the absorbent fibers was observed which could enhance the absorbent capacity and wicking rate of the absorbent member. It is believed that this occurs because the absorbent fibers are oriented, to a large extent, in the horizontal plane but with some modest "z" direction to the fiber axis as they conform to an irregular surface of the forming wire.
Today, there are a number of applications for absorbent products, both disposable and reusable, which can take advantage of the expansion properties of the absorbent. For example, an absorbent having a rapid expansion capability primarily in one direction can be used in an infant diaper to form a gasket with the legs of the infants as the absorbent expands. This decreases the chance of leakage through the leg cuffs. A second example is the use of an absorbent pad in conjunction with a retail package containing perishable food, i.e. meats and poultry. As the food item gives up juices, blood, water, and other liquids, the absorbent pad can quickly expand to absorb this fluid so that an appealing retail package of food can be presented to the consumer. Still another example is the absorbent material that is placed between the joint of two abutting pipe flanges to provide a water tight seal. The use of an absorbent with tremendous expansion capabilities is advantageous in this situation for it assure that as the absorbent swells, the gasket or seal will become tighter and prevent leakage.
Now it has been recognized that there is a real need for an absorbent member to be used in an absorbent article which has a high absorbent capacity, a high wicking rate and the ability to rapidly expand in at least one direction when wetted by an aqueous fluid.